Add ACS-IR 2.1

The ACS-IR 2.1 sequence files are identical to the ones in the ACS-IR 2.0;
add them for completeness.

- Add the ACS-IR v23.09_2.1.0 sequence files into the contrib folder.
- Update the seq_db.yaml to identify the files from the ACS-IR 2.1.
- Rename the ir2 unit test.

Signed-off-by: Vincent Stehlé <vincent.stehle@arm.com>